1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a TCP (Tape Carrier Package) structure in which semiconductor elements are mounted on an insulating tape.
2. Description of Prior Art
In a semiconductor device having a conventional TCP structure, wiring films 12 of a desired pattern composed of semiconductor films are formed on the surface of a TCP tape 11, a device hole 19 larger than a semiconductor element 15 to be mounted on the TCP tape 11 is formed in the TCP tape 11, and the internal ends 12a of the wiring films 12 are extended into the device hole 19, as shown in FIGS. 1A and 1B, which are a plan view and a line 1B--1B enlarged cross-sectional view of an example of such a device. The semiconductor element 15 is positioned inside the device hole 19 on the reverse side of the TCP tape 11, and an electrode pad 16 disposed along the peripheral portions of the semiconductor element 15 is connected to the internal ends 12a of the wiring films 12. In addition, the semiconductor element 15, the TCP wiring films 12, and the TCP tape 11 are sealed with a resin 18. 13 is a protective film that covers the wiring films 12, and 14 are sprocket holes for advancing the TCP tape 11.
A disadvantage of a semiconductor device with such a conventional structure is that because a device hole 19 is bored in the TCP tape 11 in order to mount the semiconductor element 15, a punch die is needed to form the device hole 19, expenses are made for this equipment, and costs are increased due to the need to perform punching operations. In addition, forming the device hole 19 inevitably leads to arranging the internal ends 12a of the wiring films 12 along the peripheral portions of the device hole 19, and the surface area occupied by the device hole 19 and the wiring films 12 on the TCP tape 11 increases in the longitudinal direction of the tape when the wiring films 12 are extended further outward beyond the peripheral portions in order to obtain the necessary wiring pitch interval, making the surface area needed for the TCP tape 11 larger than the size of the semiconductor element 15. In particular, there is a danger that the length of the TCP tape in the longitudinal direction will increase, and the cost of the TCP tape will rise.
In such cases, it was proposed, as in the technique described in Japanese Laid-Open Patent Application 2-205328, to place an electrode pad for a semiconductor element in the center of the element and to position the internal ends of the wiring films of a TCP tape near the center, thereby preventing the outer peripheral portions of the wiring layer from extending outward while maintaining the length of the layer above a prescribed level. Increasing the length of the internal ends of a wiring layer inside the device hole, however, makes it more likely that the wiring layer will be deformed by the weight of the semiconductor element and ultimately lowers the reliability of the connection between the semiconductor element and the wiring layer.
With conventional semiconductor devices, however, wiring films are commonly formed by etching process on the surface of the TCP tape 11 after the device hole 19 has been punched out in the TCP tape 11, creating a danger that the wiring will be shorted if etching fails to provide sufficient processing accuracy. In addition, the wiring films are not aligned properly with the pads of semiconductor elements to be connected thereto, and electrical connections sometimes cannot properly be formed when the punching accuracy of the device hole is low. Yet another disadvantage is that touch shorts occur due to the contact of wiring layers with the edges of the semiconductor elements.